This invention relates to clarifiers and in particular relates to a rectangular clarifier having a settled sludge pickup tube and a scum skimming trough.
Clarifiers are a type of gravity sedimentation device and are generally employed with dilute suspensions, principally industrial and domestic wastes, and their primary purpose is to produce a relatively clear overflow.
A typical rectangular clarifier has a chain type drag which pulls sludge from the bottom and deposits it in a sludge hopper along one wall of the clarifier. A revolving scum skimmer can be used with this type installation or the drag flights can act as scum skimmers on their return across the top of the clarifier.
A typical circular clarifier has a rotating superstructure from which is suspended a series of rake arms which move across the bottom of the clarifier and move the solids toward a sludge sump located at the center of the clarifier bottom. A rotating scum skimmer can be incorporated into a circular clarifier as well.
Circular mechanisms also have been modified to fit into square clarifier tanks by adding hinged corner blades to the rake arms to sweep the corners that lie outside the path of the main mechanism.
Accordingly, it is a principal object of the present invention to provide a rectangular clarifier having a combination sludge and scum removal device which includes a hollow main tube positioned at the center of the clarifier along the long axis and partially submerged in the clarifier liquid. The main tube rocks back and forth so that the entire bottom of the clarifier is covered by hollow sludge withdrawal tubes which are open at the bottom and connected to the hollow main tube to remove the sludge by differential head pressure which forces settled sludge up the withdrawal tubes into the main tube while the scum is picked up from the top of the clarifier liquid by an open decanter top extension on the main tube.
It is another object to provide a rectangular clarifier of small size, i.e., 1,000,000-2,000,000 gal/day capacity and a maximum width of about 20 feet for a single sludge and scum removal device. It is contemplated that a series of clarifier units can be linked together in a single housing and single sludge pit to provide increased capacity.
Still another object is to provide a rectangular clarifier in which the flow of sludge in the withdrawal tubes can be adjusted by moving the open end of the tube toward or away from the floor of the clarifier.
A further object is to provide a rectangular clarifier which can be adjusted from a combined sludge removal and scum skimming function to just a sludge removal function.
These and other objects and advantages will become apparent hereinafter.
The present invention comprises a rectangular clarifier having the capacity of removing solids from the floor of the clarifier basin by differential pressure while simultaneously skimming floating liquids from the top surface of the liquid in the clarifier.